There's a few of us who oar it on the weekends,once its flowing. We usually do Stevens (uppermish,lowermish,PoudrePark,Bridges) down,it makes for an exciting day. Lowest we've done it was 2ft. Definitely doable at that level,but there are some parts where it gets VERY bony and you'll be dodgin rock. Mostly on Lower Mish,also Tunnel gets pretty rocky at that level. I'd def. wait til about 3.5 to 4ft to go do the Rustics. 4ft for Upper Rustic.
I don't know if Filter will have enough water in it this weekend or not. It's kind've like the Lower-mish and upper Rustic section--in that it requires a little bit more water(whitewaters not the same) in them,esp. in the long straight-away below MadDog(fuzzy bunny) rapid. You might get bored on FP,its just short and not much action in a raft--and its the most crowded.....usually.
Looking at the parking lot on a weekend at Picnic Rock is way more scarier than Filter Plant